Type aliases: Typedefs for non-function types

[mit-mit]

Realizes #66, Feature specification

Sample typedef & usage:

typedef IntList = List<int>;
IntList il = [1,2,3];

Related issues: dart-lang/sdk#2626

[eernstg]

Specification CL at https://dart-review.googlesource.com/c/sdk/+/81414.

[eernstg]

Feature specification proposal in this PR.

[eernstg]

Said feature specification landed as efdc2fa.

[eernstg]

PR created for the feature specification: One rule needs to be discussed, and the right thing to do is to say explicitly that no conclusion has been reached yet, with respect to that particular rule.

[leafpetersen]

I opened an issue for discussion of the question of using typedefs where classes are expected here.

[eernstg]

Said PR now landed.

[leafpetersen]

I think we need to update the spec to reflect the consensus on static method access.

[eernstg]

Landed #116 for that.